Chi sao can be considered a drill for developing sensitivity to positioning and vulnerabilities within a quasi-sparring context. Under that definition, I would add:

Wrestling's head position drills and handfighting, as well as judo's gripfighting all have a similar goal to chi sao (finding a dominant position so that one can attack freely) and emphasize sensing vulnerable positions

Shaolin (Chi Sim) Weng Chun (which is not the same style as Wing Chun) also has chi sao, although it's a bit more like Tai chi's pushing hands.

Chi Sim Weng Chun has chi sao sets
(looping through several certain moves following each other) as well as 'free' or open chi sao. It's a practice with semi-relaxed arms 'twirling' around each other where you try, without using force, to find the right opening and hit the opponent. In this way it's similar to other chi sao/pushing hands exercises I suppose. It is fairly similar to taichi pushing hands.
To get a better idea, watch these example videos: vid1 | vid2.

I don't think there's any style besides Wing Chun that works from the center line, though.

Several martial systems contain drills to improve sensitivity with varying degrees of systemisation and formality. As a result, they have a different flavour from the chi sao in Wing Chun, but they each have a similar purpose: to build sensitivity and awareness.

Specific examples:

Taiji has "push hands" drills that involve one or both hands. (YouTube demo.)

Other arts such as Aikido contain many sensitivity drills, but they're often ingrained into the philosophy of the art as a whole, which means they don't look anything like chi sao or push hands. They're less static and formalised, and they involve full body movement rather than isolation of the upper body. (YouTube demo.)